Porthcurno beach submarine cable 1906

The global communications network depends in a large part on the undersea cables that criss-cross the planet's seabeds, capable of carrying more than 50 million phone calls simultaneously. Those cables have been around for about 150 years; here is a look back at the early days in contrast to the present.

Pictured above is the beach at Porthcurno in Cornwall on the 6 August, 1906, where workers are laying a submarine telegraph cable to Fayal in the Azores.

The very first transatlantic telegraph cable was laid in 1858. Queen Victoria telegraphed US president James Buchanan to express her congratulations and her fervent wish that the cable "will prove an additional link between the two places whose friendship is founded upon their common interests and reciprocal esteem".

Rather unfortunately, the cable was destroyed in an accident not long after. A permanent link was established in 1866, when a new cable was unspooled over the seabed by Isambard Kingdom Brunel's ship the SS Great Eastern.

Submarine cable 1906 workers

Workers (above) in 1906 tend to the cable at Porthcurno beach.

With the completion of the telegraph line to Bombay in 1870 — which was also laid by the SS Great Eastern — Porthcurno became the epicentre of international communications. For almost 100 years, it was home to one of the world's largest telegraph stations and a training college.

Ship recovers submarine cable

Workers lay a modern-day cable (above).

There are now around 250 submarine systems in operation, with another 19 due to come online in 2011.

The technology has evolved significantly since the cables of the 19th century. In 1870, the telegraph system could transmit around 10 words a minute. Today, fibre submarine cables can handle 8.4 billion words a second.

(Image: Cable & Wireless Worldwide)

Submarine cable reeled in to ship

In other respects, the science of laying submarine cables has barely changed from the early days.

The method of recovering cables for repairs is essentially the same — it consists of using a grappling hook on the end of a rope up to five miles long.

According to Cable & Wireless Worldwide — the company that has inherited much of the world's submarine infrastructure — the rope used today is often more expensive than the cable it recovers.

(Image: Cable & Wireless Worldwide)

Submarine cable modern day

Cable & Wireless Worldwide estimates that its submarine network now stretches to around 500,000km, far greater than the distance between the Earth and the moon.

The company can trace its history back to a consortium led by Sir John Pender in the 1860s, which oversaw the establishment of the first transatlantic cable.

Given the vital role undersea cables have played in tying the world together, it is worth bearing in mind President Buchanan's reply to Queen Victoria's telegraph on the first transatlantic cable: "It is a triumph more glorious, because far more useful to mankind, than was ever won by conqueror on the field of battle."

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Submarine cable 1906 workers

Workers (above) in 1906 tend to the cable at Porthcurno beach.

With the completion of the telegraph line to Bombay in 1870 — which was also laid by the SS Great Eastern — Porthcurno became the epicentre of international communications. For almost 100 years, it was home to one of the world's largest telegraph stations and a training college.